Added some handling for when the user tries to do an export with a bogus output_id
Added some handling for when the user tries to do an export with a bogus output_id


Former-commit-id: b4a7ebf8659b17fa0147a3cb657072e833fee87d
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine